1. Field of the Invention
This invention relates to a golf club shaft and a production method thereof.
2. Description of the Prior Art
Recently, golf clubs provided with shafts made of fiber reinforced synthetic resin or synthetic resin have been developed, such as the one described in Japanese Utility Model Laid-open No. 63-46169.
FIG. 4 and FIG. 5 illustrate this conventional type of golf club shaft, in which 11 is an inner layer formed by winding prepreg sheets, or high-strength fiber impregnated with matrix.
The inner layer 11 has its periphery wound with a middle layer 13, and the middle layer 13 with a string member 15 made of amorphous fiber, carbon fiber or Kevlar fiber in the form of mesh.
The string member 15 is wound with prepreg sheets as an outer layer 17, comprising fiber and matrix which become transparent after curing, for example sheets of glass cloth.
As shown in FIG. 6, the conventional club shaft as described above has layers in good condition until the outer layer 17 is wound, but suffers zigzag A or wrinkles B on the string member 15 or mesh fiber 19 which forms the outer layer 17, after taping or curing, as shown in FIG. 7 and FIG. 8.
Another problem is sagging or whitening, which hides the braiding pattern formed by the string member 15 as shown in FIG. 8 C. In addition, when the surface of the outer layer 17 is polished, texture of the fiber 19 in the outer layer 17 can be seen depending on the direction of light, which results in defective appearance and sometimes declined strength.